1. Field of the Invention
The invention relates to a medical device comprising a radially compressible and expandable lattice structure. Devices of this kind are known from practice, for example, in the form of stents or emboli traps.
2. Background Art
Known stents comprise a lattice structure, which is formed from cells. The cells are delimited by interconnected webs. In particular, stents are known that are cut from tubes, for example, by laser cutting.
Stents are generally radially compressible and expandable. For introduction into a blood vessel, the stent is guided via a catheter in a compressed state. After leaving the catheter, the stent opens up or expands and adapts itself to the vessel wall. At the same time, the stent attempts to adopt a circular cylindrical shape. In other words, the stent expands radially uniformly.
The radially uniform expansion of the stent is comparatively unproblematic in straight blood vessels. However, it has been found that when stents are used in curved blood vessels, forces develop that can impede uniform radial expansion of the stent. In particular, the stent expands more strongly in the transverse direction, i.e. parallel to the axis of curvature of the blood vessel, than in a direction perpendicular to the axis of curvature of the blood vessel. In other words, in vessel curvatures, a substantially oval cross-sectional profile of the stent is established. Therefore, there is a risk of the stent exerting different radial forces on some sections of the vessel wall. This can result in additional local irritation of the vessel walls. There is also a risk of gaps forming between the lattice structure of the stent and the blood vessel in some sections. Since, the lattice structure influences the blood flow in the region between the lattice structure and the blood-vessel wall, this can result in the formation of blood clots.